Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, Prague 16200, Czech Republic.
Phys Chem Chem Phys. 2019 Jan 21;21(3):1564-1571. doi: 10.1039/c8cp06290k. Epub 2019 Jan 8.
We use inelastic electron tunneling spectroscopy (IETS) first-principles simulations to identify and characterize the different vibrational modes of single conjugated molecules bonded to Au metal electrodes. The molecules are polyphenyls (with 1 to 4 benzene units) bonded to Au via highly conducting direct Au-C bonds. The short molecule shows near resonant elastic transmission, with a crossover to tunneling for the longer backbones. The calculated inelastic spectra exhibit dips in the IETS signal of the short molecule and peaks for the longer molecules. We characterize the symmetry of vibrational modes and scattering states and discuss the changes with increasing length, where the inelastic signal of different modes can be amplified, quenched or present a crossover as more benzene units are added to the molecular backbone. This analysis rationalizes the observed trends as a function of molecular length and illustrates the role of electronic and vibrational properties on Au-C bonded molecular junctions.
我们使用非弹性电子隧道谱（IETS）第一性原理模拟来识别和表征键合到 Au 金属电极的单个共轭分子的不同振动模式。这些分子是通过高导电性的直接 Au-C 键与 Au 键合的多苯基（具有 1 到 4 个苯单元）。短分子表现出近共振弹性传输，对于较长的骨架则转变为隧道传输。计算出的非弹性谱在短分子的 IETS 信号中出现下降，而在较长分子中出现峰值。我们对振动模式和散射态的对称性进行了特征化，并讨论了随着长度的增加而发生的变化，其中随着更多苯单元添加到分子骨架，不同模式的非弹性信号可以被放大、猝灭或出现交叉。这种分析从分子长度的函数上合理地解释了观察到的趋势，并说明了电子和振动特性在 Au-C 键合分子结中的作用。
